This invention relates generally to systems for controlling the rf energy beam pattern for a communication satellite, and, more particularly, to systems for configuring an array of rf switches that feed rf energy to or from an array of -antenna feed horns.
A typical communication satellite includes one or more generally spherical or parabolic "dish" antenna reflectors for receiving and transmitting the beams of electromagnetic radiation. Many applications require the satellite to be maintained in a stationary orbit, approximately 22,300 miles above the earth's surface, with the satellite antenna reflectors continuously viewing particular geographical regions of the earth. The satellite usually has one antenna reflector for receiving an rf signal from the earth, and a separate antenna reflector for transmitting a separate rf signal back to the earth. The receiving reflector focuses the received signal onto an array of discrete feed elements, such as receive feed horns, positioned in the reflector's focal plane. Similarly, the rf signal transmitted by the transmitting reflector is provided by a similarly-aligned array of transmit feed horns.
By virtue of its particular location in the focal plane of the antenna reflector, each individual feed horn produces or receives a beam that illuminates a particular part of the earth. An entire array of feed horns, which can consist of as many as 90 feed horns, can illuminate a wide region on the earth. By activating or deactivating selected feed horns in the array, different zones of the earth can be selectively illuminated. In some satellites, the array of feed horns provides selective hemispheric coverage of three different zones, and reconfiguring of each zone pattern is controlled by an array of rf switches, each connected to a separate feed horn.
Simultaneous rotation of the rf switches to one of three positions redistributes the excitation to the feed horn array and controls the beam pattern of the antenna reflector. When reconfiguring the zone patterns, it is desirable to operate all of the rf switches at the same time, to instantaneously produce a pattern change. Thus, a switch positioner preferably rotates the switches in unison to one of three positions, to activate or deactivate selected horns and create a predetermined pattern of beam coverage for a particular zone on the earth.
Accordingly, there has existed a definite need for a switch positioner apparatus that simultaneously rotates a plurality of switches, to control the input and output of an array of satellite feed horns. The switch positioner apparatus should preferably be light in weight and small in size, and should provide reliability and redundancy in operation.